1
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Xu C, Wu X, Qiu J, Ye J, Lin Q, Deng J, Zeng Y, Wang W, Zhang H, Zheng H. Genome-wide identification of gap junction gene family and their expression profiles under low temperature stress in noble scallop Chlamys nobilis. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART D, GENOMICS & PROTEOMICS 2024; 52:101310. [PMID: 39137603 DOI: 10.1016/j.cbd.2024.101310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2024] [Revised: 07/13/2024] [Accepted: 08/08/2024] [Indexed: 08/15/2024]
Abstract
Gap junctions, formed by gap junction proteins (GJ), play crucial roles in cell signaling and immune responses. The structure and function of the GJ from vertebrates (called connexins) have been extensively studied. However, little is known about the proteins forming gap junctions in invertebrates (called innexins). In this study, 14 GJ genes of Chlamys nobilis were identified. GJ proteins are mainly distributed on the plasma membrane, and all proteins are hydrophilic Phylogenetic tree analysis showed that the GJ proteins in C. nobilis were distantly related to those in vertebrates but closely related to those in invertebrates. Conserved motifs analysis of these GJ proteins in C. nobilis identified to have 10 conserved motifs, similar to gap junction proteins in other bivalves. Moreover, expression profiles of CnGJ genes under chronic and acute low temperature stress were also investigated. Results showed that chronic low temperature stress had a significant effect on the expression levels of CnGJ genes, and the expression profiles of CnGJ genes showed significantly variation under acute low temperature stress. All these results indicated that CnGJ genes play important roles in environmental adaptation in scallops. The present study initially elucidated the function of gap junction genes in noble scallop C. nobilis, which provides new insights into the GJ genes in mollusks and will help us better understand their roles in environmental stress in scallops.
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Affiliation(s)
- Changping Xu
- Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China; Research Center of Engineering Technology for Subtropical Mariculture of Guangdong Province, Shantou 515063, China; STU-UMT Joint Shellfish Research Laboratory, Shantou University, Shantou 515063, China
| | - Xuanbing Wu
- Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China; Research Center of Engineering Technology for Subtropical Mariculture of Guangdong Province, Shantou 515063, China; STU-UMT Joint Shellfish Research Laboratory, Shantou University, Shantou 515063, China
| | - Jiale Qiu
- Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China; Research Center of Engineering Technology for Subtropical Mariculture of Guangdong Province, Shantou 515063, China; STU-UMT Joint Shellfish Research Laboratory, Shantou University, Shantou 515063, China
| | - Jianming Ye
- Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China; Research Center of Engineering Technology for Subtropical Mariculture of Guangdong Province, Shantou 515063, China; STU-UMT Joint Shellfish Research Laboratory, Shantou University, Shantou 515063, China
| | - Qing Lin
- Shantou Fruit Tree and Aquatic Technology Promotion Station, Shantou 515063, China
| | - Jingwen Deng
- Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China; Research Center of Engineering Technology for Subtropical Mariculture of Guangdong Province, Shantou 515063, China; STU-UMT Joint Shellfish Research Laboratory, Shantou University, Shantou 515063, China
| | - Yetao Zeng
- Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China; Research Center of Engineering Technology for Subtropical Mariculture of Guangdong Province, Shantou 515063, China; STU-UMT Joint Shellfish Research Laboratory, Shantou University, Shantou 515063, China
| | - Weili Wang
- Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China; Research Center of Engineering Technology for Subtropical Mariculture of Guangdong Province, Shantou 515063, China; STU-UMT Joint Shellfish Research Laboratory, Shantou University, Shantou 515063, China
| | - Hongkuan Zhang
- Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China; Research Center of Engineering Technology for Subtropical Mariculture of Guangdong Province, Shantou 515063, China; STU-UMT Joint Shellfish Research Laboratory, Shantou University, Shantou 515063, China.
| | - Huaiping Zheng
- Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China; Research Center of Engineering Technology for Subtropical Mariculture of Guangdong Province, Shantou 515063, China; STU-UMT Joint Shellfish Research Laboratory, Shantou University, Shantou 515063, China.
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2
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Nakayama A, Watanabe M, Yamashiro R, Kuroyanagi H, Matsuyama HJ, Oshima A, Mori I, Nakano S. A hyperpolarizing neuron recruits undocked innexin hemichannels to transmit neural information in Caenorhabditis elegans. Proc Natl Acad Sci U S A 2024; 121:e2406565121. [PMID: 38753507 PMCID: PMC11127054 DOI: 10.1073/pnas.2406565121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Accepted: 04/19/2024] [Indexed: 05/18/2024] Open
Abstract
While depolarization of the neuronal membrane is known to evoke the neurotransmitter release from synaptic vesicles, hyperpolarization is regarded as a resting state of chemical neurotransmission. Here, we report that hyperpolarizing neurons can actively signal neural information by employing undocked hemichannels. We show that UNC-7, a member of the innexin family in Caenorhabditis elegans, functions as a hemichannel in thermosensory neurons and transmits temperature information from the thermosensory neurons to their postsynaptic interneurons. By monitoring neural activities in freely behaving animals, we find that hyperpolarizing thermosensory neurons inhibit the activity of the interneurons and that UNC-7 hemichannels regulate this process. UNC-7 is required to control thermotaxis behavior and functions independently of synaptic vesicle exocytosis. Our findings suggest that innexin hemichannels mediate neurotransmission from hyperpolarizing neurons in a manner that is distinct from the synaptic transmission, expanding the way of neural circuitry operations.
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Affiliation(s)
- Airi Nakayama
- Department of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi464-8602, Japan
| | - Masakatsu Watanabe
- Laboratory of Pattern Formation, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka565-0871, Japan
| | - Riku Yamashiro
- Department of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi464-8602, Japan
| | - Hiroo Kuroyanagi
- Department of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi464-8602, Japan
| | - Hironori J. Matsuyama
- Group of Molecular Neurobiology, Neuroscience Institute, Graduate School of Science, Nagoya University, Nagoya, Aichi464-8602, Japan
| | - Atsunori Oshima
- Department of Basic Biology, Cellular and Structural Physiology Institute, Nagoya University, Chikusa, Nagoya464-8601, Japan
- Department of Basic Medicinal Sciences, Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, Aichi464-8601, Japan
- Molecular Physiology Division, Institute for Glyco-core Research, Nagoya University, Chikusa-ku, Nagoya464-8601, Japan
- Division of Innovative Modality Development, Center for One Medicine Innovative Translational Research, Gifu University Institute for Advanced Study, Gifu501-11193, Japan
| | - Ikue Mori
- Group of Molecular Neurobiology, Neuroscience Institute, Graduate School of Science, Nagoya University, Nagoya, Aichi464-8602, Japan
- Chinese Institute for Brain Research, Changping District, Beijing102206, China
| | - Shunji Nakano
- Department of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi464-8602, Japan
- Group of Molecular Neurobiology, Neuroscience Institute, Graduate School of Science, Nagoya University, Nagoya, Aichi464-8602, Japan
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3
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Majeed M, Han H, Zhang K, Cao WX, Liao CP, Hobert O, Lu H. Toolkits for detailed and high-throughput interrogation of synapses in C. elegans. eLife 2024; 12:RP91775. [PMID: 38224479 PMCID: PMC10945580 DOI: 10.7554/elife.91775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2024] Open
Abstract
Visualizing synaptic connectivity has traditionally relied on time-consuming electron microscopy-based imaging approaches. To scale the analysis of synaptic connectivity, fluorescent protein-based techniques have been established, ranging from the labeling of specific pre- or post-synaptic components of chemical or electrical synapses to transsynaptic proximity labeling technology such as GRASP and iBLINC. In this paper, we describe WormPsyQi, a generalizable image analysis pipeline that automatically quantifies synaptically localized fluorescent signals in a high-throughput and robust manner, with reduced human bias. We also present a resource of 30 transgenic strains that label chemical or electrical synapses throughout the nervous system of the nematode Caenorhabditis elegans, using CLA-1, RAB-3, GRASP (chemical synapses), or innexin (electrical synapse) reporters. We show that WormPsyQi captures synaptic structures in spite of substantial heterogeneity in neurite morphology, fluorescence signal, and imaging parameters. We use these toolkits to quantify multiple obvious and subtle features of synapses - such as number, size, intensity, and spatial distribution of synapses - in datasets spanning various regions of the nervous system, developmental stages, and sexes. Although the pipeline is described in the context of synapses, it may be utilized for other 'punctate' signals, such as fluorescently tagged neurotransmitter receptors and cell adhesion molecules, as well as proteins in other subcellular contexts. By overcoming constraints on time, sample size, cell morphology, and phenotypic space, this work represents a powerful resource for further analysis of synapse biology in C. elegans.
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Affiliation(s)
- Maryam Majeed
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia UniversityNew YorkUnited States
| | - Haejun Han
- School of Electrical and Computer Engineering, Georgia Institute of TechnologyAtlantaUnited States
- The Parker H Petit Institute of Bioengineering and Bioscience, Georgia Institute of TechnologyAtlantaUnited States
| | - Keren Zhang
- School of Chemical and Biomolecular Engineering, Georgia Institute of TechnologyAtlantaUnited States
| | - Wen Xi Cao
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia UniversityNew YorkUnited States
| | - Chien-Po Liao
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia UniversityNew YorkUnited States
| | - Oliver Hobert
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia UniversityNew YorkUnited States
| | - Hang Lu
- The Parker H Petit Institute of Bioengineering and Bioscience, Georgia Institute of TechnologyAtlantaUnited States
- School of Chemical and Biomolecular Engineering, Georgia Institute of TechnologyAtlantaUnited States
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4
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Hendi A, Niu LG, Snow AW, Ikegami R, Wang ZW, Mizumoto K. Channel-independent function of UNC-9/Innexin in spatial arrangement of GABAergic synapses in C. elegans. eLife 2022; 11:80555. [PMID: 36378164 PMCID: PMC9665852 DOI: 10.7554/elife.80555] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 11/03/2022] [Indexed: 11/16/2022] Open
Abstract
Precise synaptic connection of neurons with their targets is essential for the proper functioning of the nervous system. A plethora of signaling pathways act in concert to mediate the precise spatial arrangement of synaptic connections. Here we show a novel role for a gap junction protein in controlling tiled synaptic arrangement in the GABAergic motor neurons in Caenorhabditis elegans, in which their axons and synapses overlap minimally with their neighboring neurons within the same class. We found that while EGL-20/Wnt controls axonal tiling, their presynaptic tiling is mediated by a gap junction protein UNC-9/Innexin, that is localized at the presynaptic tiling border between neighboring dorsal D-type GABAergic motor neurons. Strikingly, the gap junction channel activity of UNC-9 is dispensable for its function in controlling tiled presynaptic patterning. While gap junctions are crucial for the proper functioning of the nervous system as channels, our finding uncovered the novel channel-independent role of UNC-9 in synapse patterning.
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Affiliation(s)
- Ardalan Hendi
- Department of Zoology, University of British Columbia
- Life Sciences Institute, University of British Columbia
| | - Long-Gang Niu
- Department of Neuroscience, University of Connecticut Health Center
| | - Andrew William Snow
- Graduate Program in Cell and Developmental Biology, University of British Columbia
| | | | - Zhao-Wen Wang
- Department of Neuroscience, University of Connecticut Health Center
| | - Kota Mizumoto
- Department of Zoology, University of British Columbia
- Life Sciences Institute, University of British Columbia
- Graduate Program in Cell and Developmental Biology, University of British Columbia
- Djavad Mowafaghian Centre for Brain Health, University of British Columbia
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5
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Rapti G. A perspective on C. elegans neurodevelopment: from early visionaries to a booming neuroscience research. J Neurogenet 2021; 34:259-272. [PMID: 33446023 DOI: 10.1080/01677063.2020.1837799] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The formation of the nervous system and its striking complexity is a remarkable feat of development. C. elegans served as a unique model to dissect the molecular events in neurodevelopment, from its early visionaries to the current booming neuroscience community. Soon after being introduced as a model, C. elegans was mapped at the level of genes, cells, and synapses, providing the first metazoan with a complete cell lineage, sequenced genome, and connectome. Here, I summarize mechanisms underlying C. elegans neurodevelopment, from the generation and diversification of neural components to their navigation and connectivity. I point out recent noteworthy findings in the fields of glia biology, sex dimorphism and plasticity in neurodevelopment, highlighting how current research connects back to the pioneering studies by Brenner, Sulston and colleagues. Multifaceted investigations in model organisms, connecting genes to cell function and behavior, expand our mechanistic understanding of neurodevelopment while allowing us to formulate emerging questions for future discoveries.
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Affiliation(s)
- Georgia Rapti
- European Molecular Biology Laboratory, Unit of Developmental Biology, Heidelberg, Germany
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6
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Meng L, Yan D. NLR-1/CASPR Anchors F-Actin to Promote Gap Junction Formation. Dev Cell 2020; 55:574-587.e3. [PMID: 33238150 DOI: 10.1016/j.devcel.2020.10.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Revised: 08/05/2020] [Accepted: 10/28/2020] [Indexed: 12/31/2022]
Abstract
Gap junctions are present in most tissues and play essential roles in various biological processes. However, we know surprisingly little about the molecular mechanisms underlying gap junction formation. Here, we uncover the essential role of a conserved EGF- and laminin-G-domain-containing protein nlr-1/CASPR in the regulation of gap junction formation in multiple tissues across different developmental stages in C. elegans. NLR-1 is located in the gap junction perinexus, a region adjacent to but not overlapping with gap junctions, and forms puncta before the clusters of gap junction channels appear on the membrane. We show that NLR-1 can directly bind to actin to recruit F-actin networks at the gap junction formation plaque, and the formation of F-actin patches plays a critical role in the assembly of gap junction channels. Our findings demonstrate that nlr-1/CASPR acts as an early stage signal for gap junction formation through anchoring of F-actin networks.
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Affiliation(s)
- Lingfeng Meng
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Dong Yan
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA; Department of Neurobiology, Regeneration Next, and Duke Institute for Brain Sciences, Duke University Medical Center, Durham, NC 27710, USA.
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7
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Jin EJ, Park S, Lyu X, Jin Y. Gap junctions: historical discoveries and new findings in the Caenorhabditiselegans nervous system. Biol Open 2020; 9:bio053983. [PMID: 32883654 PMCID: PMC7489761 DOI: 10.1242/bio.053983] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Gap junctions are evolutionarily conserved structures at close membrane contacts between two cells. In the nervous system, they mediate rapid, often bi-directional, transmission of signals through channels called innexins in invertebrates and connexins in vertebrates. Connectomic studies from Caenorhabditis elegans have uncovered a vast number of gap junctions present in the nervous system and non-neuronal tissues. The genome also has 25 innexin genes that are expressed in spatial and temporal dynamic pattern. Recent findings have begun to reveal novel roles of innexins in the regulation of multiple processes during formation and function of neural circuits both in normal conditions and under stress. Here, we highlight the diverse roles of gap junctions and innexins in the C. elegans nervous system. These findings contribute to fundamental understanding of gap junctions in all animals.
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Affiliation(s)
- Eugene Jennifer Jin
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Seungmee Park
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Xiaohui Lyu
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Yishi Jin
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
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8
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Mulcahy B, Witvliet D, Holmyard D, Mitchell J, Chisholm AD, Meirovitch Y, Samuel ADT, Zhen M. A Pipeline for Volume Electron Microscopy of the Caenorhabditis elegans Nervous System. Front Neural Circuits 2018; 12:94. [PMID: 30524248 PMCID: PMC6262311 DOI: 10.3389/fncir.2018.00094] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Accepted: 10/08/2018] [Indexed: 01/01/2023] Open
Abstract
The “connectome,” a comprehensive wiring diagram of synaptic connectivity, is achieved through volume electron microscopy (vEM) analysis of an entire nervous system and all associated non-neuronal tissues. White et al. (1986) pioneered the fully manual reconstruction of a connectome using Caenorhabditis elegans. Recent advances in vEM allow mapping new C. elegans connectomes with increased throughput, and reduced subjectivity. Current vEM studies aim to not only fill the remaining gaps in the original connectome, but also address fundamental questions including how the connectome changes during development, the nature of individuality, sexual dimorphism, and how genetic and environmental factors regulate connectivity. Here we describe our current vEM pipeline and projected improvements for the study of the C. elegans nervous system and beyond.
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Affiliation(s)
- Ben Mulcahy
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada
| | - Daniel Witvliet
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Douglas Holmyard
- Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, ON, Canada.,Nanoscale Biomedical Imaging Facility, The Hospital for Sick Children, Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
| | - James Mitchell
- Center for Brain Science, Department of Physics, Harvard University, Cambridge, MA, United States
| | - Andrew D Chisholm
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA, United States
| | - Yaron Meirovitch
- Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Aravinthan D T Samuel
- Center for Brain Science, Department of Physics, Harvard University, Cambridge, MA, United States
| | - Mei Zhen
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada.,Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
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9
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Güiza J, Barría I, Sáez JC, Vega JL. Innexins: Expression, Regulation, and Functions. Front Physiol 2018; 9:1414. [PMID: 30364195 PMCID: PMC6193117 DOI: 10.3389/fphys.2018.01414] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 09/18/2018] [Indexed: 01/02/2023] Open
Abstract
The innexin (Inx) proteins form gap junction channels and non-junctional channels (named hemichannels) in invertebrates. These channels participate in cellular communication playing a relevant role in several physiological processes. Pioneer studies conducted mainly in worms and flies have shown that innexins participate in embryo development and behavior. However, recent studies have elucidated new functions of innexins in Arthropoda, Nematoda, Annelida, and Cnidaria, such as immune response, and apoptosis. This review describes emerging data of possible new roles of innexins and summarizes the data available to date.
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Affiliation(s)
- Juan Güiza
- Laboratorio de Fisiología Experimental, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
| | - Iván Barría
- Laboratorio de Fisiología Experimental, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
| | - Juan C Sáez
- Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago, Chile.,Instituto de Neurociencias, Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - José L Vega
- Laboratorio de Fisiología Experimental, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
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10
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The role of gap junctions in the C. elegans connectome. Neurosci Lett 2017; 695:12-18. [PMID: 28886984 DOI: 10.1016/j.neulet.2017.09.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 07/12/2017] [Accepted: 09/01/2017] [Indexed: 10/18/2022]
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11
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Meng L, Zhang A, Jin Y, Yan D. Regulation of neuronal axon specification by glia-neuron gap junctions in C. elegans. eLife 2016; 5. [PMID: 27767956 PMCID: PMC5083064 DOI: 10.7554/elife.19510] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 10/20/2016] [Indexed: 01/22/2023] Open
Abstract
Axon specification is a critical step in neuronal development, and the function of glial cells in this process is not fully understood. Here, we show that C. elegans GLR glial cells regulate axon specification of their nearby GABAergic RME neurons through GLR-RME gap junctions. Disruption of GLR-RME gap junctions causes misaccumulation of axonal markers in non-axonal neurites of RME neurons and converts microtubules in those neurites to form an axon-like assembly. We further uncover that GLR-RME gap junctions regulate RME axon specification through activation of the CDK-5 pathway in a calcium-dependent manner, involving a calpain clp-4. Therefore, our study reveals the function of glia-neuron gap junctions in neuronal axon specification and shows that calcium originated from glial cells can regulate neuronal intracellular pathways through gap junctions.
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Affiliation(s)
- Lingfeng Meng
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, United States.,Department of Neurobiology, Duke University Medical Center, Durham, United States.,Duke Institute for Brain Sciences, Duke Medical Center, Durham, United States
| | - Albert Zhang
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, United States.,Department of Neurobiology, Duke University Medical Center, Durham, United States.,Duke Institute for Brain Sciences, Duke Medical Center, Durham, United States
| | - Yishi Jin
- Neurobiology Section, Division of Biological Sciences, Howard Hughes Medical Institute, University of California, San Diego, United States.,Department of Cellular and Molecular Medicine, School of Medicine, University of California, San Diego, United States
| | - Dong Yan
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, United States.,Department of Neurobiology, Duke University Medical Center, Durham, United States.,Duke Institute for Brain Sciences, Duke Medical Center, Durham, United States
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12
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Markert SM, Britz S, Proppert S, Lang M, Witvliet D, Mulcahy B, Sauer M, Zhen M, Bessereau JL, Stigloher C. Filling the gap: adding super-resolution to array tomography for correlated ultrastructural and molecular identification of electrical synapses at the C. elegans connectome. NEUROPHOTONICS 2016; 3:041802. [PMID: 27175373 PMCID: PMC4855082 DOI: 10.1117/1.nph.3.4.041802] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 03/08/2016] [Indexed: 06/02/2023]
Abstract
Correlating molecular labeling at the ultrastructural level with high confidence remains challenging. Array tomography (AT) allows for a combination of fluorescence and electron microscopy (EM) to visualize subcellular protein localization on serial EM sections. Here, we describe an application for AT that combines near-native tissue preservation via high-pressure freezing and freeze substitution with super-resolution light microscopy and high-resolution scanning electron microscopy (SEM) analysis on the same section. We established protocols that combine SEM with structured illumination microscopy (SIM) and direct stochastic optical reconstruction microscopy (dSTORM). We devised a method for easy, precise, and unbiased correlation of EM images and super-resolution imaging data using endogenous cellular landmarks and freely available image processing software. We demonstrate that these methods allow us to identify and label gap junctions in Caenorhabditis elegans with precision and confidence, and imaging of even smaller structures is feasible. With the emergence of connectomics, these methods will allow us to fill in the gap-acquiring the correlated ultrastructural and molecular identity of electrical synapses.
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Affiliation(s)
| | - Sebastian Britz
- University of Würzburg, Biocenter, Division of Electron Microscopy, Am Hubland, Würzburg 97074, Germany
| | - Sven Proppert
- University of Würzburg, Department of Biotechnology and Biophysics, Am Hubland, Würzburg 97074, Germany
- University of Würzburg, Department of Neurophysiology, Institute of Physiology, Röntgenring 9, Würzburg 97070, Germany
| | - Marietta Lang
- University of Würzburg, Biocenter, Division of Electron Microscopy, Am Hubland, Würzburg 97074, Germany
| | - Daniel Witvliet
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada
- University of Toronto, Department of Molecular Genetics, Physiology and Institute of Medical Science, 1 King's College Cir, Toronto, Ontario M5S 1A8, Canada
| | - Ben Mulcahy
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada
- University of Toronto, Department of Molecular Genetics, Physiology and Institute of Medical Science, 1 King's College Cir, Toronto, Ontario M5S 1A8, Canada
| | - Markus Sauer
- University of Würzburg, Department of Biotechnology and Biophysics, Am Hubland, Würzburg 97074, Germany
| | - Mei Zhen
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada
- University of Toronto, Department of Molecular Genetics, Physiology and Institute of Medical Science, 1 King's College Cir, Toronto, Ontario M5S 1A8, Canada
| | - Jean-Louis Bessereau
- Institut NeuroMyoGene, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U1217, 16 rue R. Dubois, Villeurbanne Cedex F-69622, France
| | - Christian Stigloher
- University of Würzburg, Biocenter, Division of Electron Microscopy, Am Hubland, Würzburg 97074, Germany
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13
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DOP-2 D2-Like Receptor Regulates UNC-7 Innexins to Attenuate Recurrent Sensory Motor Neurons during C. elegans Copulation. J Neurosci 2015; 35:9990-10004. [PMID: 26156999 DOI: 10.1523/jneurosci.0940-15.2015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
UNLABELLED Neuromodulation of self-amplifying circuits directs context-dependent behavioral executions. Although recurrent networks are found throughout the Caenorhabditis elegans connectome, few reports describe the mechanisms that regulate reciprocal neural activity during complex behavior. We used C. elegans male copulation to dissect how a goal-oriented motor behavior is regulated by recurrently wired sensory-motor neurons. As the male tail presses against the hermaphrodite's vulva, cholinergic and glutamatergic reciprocal innervations of post cloaca sensilla (PCS) neurons (PCA, PCB, and PCC), hook neurons (HOA, HOB), and their postsynaptic sex muscles execute rhythmic copulatory spicule thrusts. These repetitive spicule movements continue until the male shifts off the vulva or genital penetration is accomplished. However, the signaling mechanism that temporally and spatially restricts repetitive intromission attempts to vulva cues was unclear. Here, we report that confinement of spicule insertion attempts to the vulva is facilitated by D2-like receptor modulation of gap-junctions between PCB and the hook sensillum. We isolated a missense mutation in the UNC-7(L) gap-junction isoform, which perturbs DOP-2 signaling in the PCB neuron and its electrical partner, HOA. The glutamate-gated chloride channel AVR-14 is expressed in HOA. Our analysis of the unc-7 mutant allele indicates that when DOP-2 promotes UNC-7 electrical communication, AVR-14-mediated inhibitory signals pass from HOA to PCB. As a consequence, PCB is less receptive to be stimulated by its recurrent synaptic partner, PCA. Behavioral observations suggest that dopamine neuromodulation of UNC-7 ensures attenuation of recursive intromission attempts when the male disengages or is dislodged from the hermaphrodite genitalia. SIGNIFICANCE STATEMENT Using C. elegans male copulation as a model, we found that the neurotransmitter dopamine stimulates D2-like receptors in two sensory circuits to terminate futile behavioral loops. The D2-like receptors promote inhibitory electrical junction activity between a chemosensory and a mechanosensory circuit. Therefore, both systems are attenuated and the animal ceases the recursive behavior.
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Meng L, Mulcahy B, Cook SJ, Neubauer M, Wan A, Jin Y, Yan D. The Cell Death Pathway Regulates Synapse Elimination through Cleavage of Gelsolin in Caenorhabditis elegans Neurons. Cell Rep 2015; 11:1737-48. [PMID: 26074078 DOI: 10.1016/j.celrep.2015.05.031] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 05/01/2015] [Accepted: 05/15/2015] [Indexed: 11/17/2022] Open
Abstract
Synapse elimination occurs in development, plasticity, and disease. Although the importance of synapse elimination has been documented in many studies, the molecular mechanisms underlying this process are unclear. Here, using the development of C. elegans RME neurons as a model, we have uncovered a function for the apoptosis pathway in synapse elimination. We find that the conserved apoptotic cell death (CED) pathway and axonal mitochondria are required for the elimination of transiently formed clusters of presynaptic components in RME neurons. This function of the CED pathway involves the activation of the actin-filament-severing protein, GSNL-1. Furthermore, we show that caspase CED-3 cleaves GSNL-1 at a conserved C-terminal region and that the cleaved active form of GSNL-1 promotes its actin-severing ability. Our data suggest that activation of the CED pathway contributes to selective elimination of synapses through disassembly of the actin filament network.
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Affiliation(s)
- Lingfeng Meng
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham, NC 27710, USA
| | - Ben Mulcahy
- Lunenfeld-Tanenbaum Research Institute, Toronto, ON M5G 1X5, Canada
| | - Steven J Cook
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Marianna Neubauer
- Department of Physics and Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Airong Wan
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham, NC 27710, USA
| | - Yishi Jin
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA; Department of Cellular and Molecular Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Dong Yan
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham, NC 27710, USA; Department of Neurobiology and Duke Institute for Brain Sciences, Duke University Medical Center, Research Drive, Durham, NC 27710, USA.
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Sangaletti R, Dahl G, Bianchi L. Mechanosensitive unpaired innexin channels in C. elegans touch neurons. Am J Physiol Cell Physiol 2014; 307:C966-77. [PMID: 25252948 DOI: 10.1152/ajpcell.00246.2014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Invertebrate innexin proteins share sequence homology with vertebrate pannexins and general membrane topology with both pannexins and connexins. While connexins form gap junctions that mediate intercellular communication, pannexins are thought to function exclusively as plasma membrane channels permeable to both ions and small molecules. Undoubtedly, certain innexins function as gap junction proteins. However, due to sequence similarity to pannexins, it was postulated that innexins also function as plasma membrane channels. Indeed, some of the leech innexins were found to mediate ATP release as unpaired membrane channels with shared pharmacology to pannexin channels. We show here that Caenorhabditis elegans touch-sensing neurons express a mechanically gated innexin channel with a conductance of ∼1 nS and voltage-dependent and K(+)-selective subconductance state. We also show that C. elegans touch neurons take up ethidium bromide through a mechanism that is activated and blocked by innexin activating stimuli and inhibitors, respectively. Finally, we present evidence that touch neurons' innexins are required for cell death induced by chemical ischemia. Our work demonstrates that innexins function as plasma membrane channels in native C. elegans neurons, where they may play a role in pathological cell death.
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Affiliation(s)
- Rachele Sangaletti
- Department of Physiology and Biophysics, University of Miami, Miller School of Medicine, Miami, Florida
| | - Gerhard Dahl
- Department of Physiology and Biophysics, University of Miami, Miller School of Medicine, Miami, Florida
| | - Laura Bianchi
- Department of Physiology and Biophysics, University of Miami, Miller School of Medicine, Miami, Florida
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16
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The F-box protein MEC-15 (FBXW9) promotes synaptic transmission in GABAergic motor neurons in C. elegans. PLoS One 2013; 8:e59132. [PMID: 23527112 PMCID: PMC3601060 DOI: 10.1371/journal.pone.0059132] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 02/11/2013] [Indexed: 11/19/2022] Open
Abstract
Ubiquitination controls the activity of many proteins and has been implicated in almost every aspect of neuronal cell biology. Characterizing the precise function of ubiquitin ligases, the enzymes that catalyze ubiquitination of target proteins, is key to understanding distinct functions of ubiquitination. F-box proteins are the variable subunits of the large family of SCF ubiquitin ligases and are responsible for binding and recognizing specific ubiquitination targets. Here, we investigated the function of the F-box protein MEC-15 (FBXW9), one of a small number of F-box proteins evolutionarily conserved from C. elegans to mammals. mec-15 is widely expressed in the nervous system including GABAergic and cholinergic motor neurons. Electrophysiological and behavioral analyses indicate that GABAergic synaptic transmission is reduced in mec-15 mutants while cholinergic transmission appears normal. In the absence of MEC-15, the abundance of the synaptic vesicle protein SNB-1 (synaptobrevin) is reduced at synapses and increased in cell bodies of GABAergic motor neurons, suggesting that MEC-15 affects the trafficking of SNB-1 between cell bodies and synapses and may promote GABA release by regulating the abundance of SNB-1 at synapses.
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17
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Oshima A, Matsuzawa T, Nishikawa K, Fujiyoshi Y. Oligomeric structure and functional characterization of Caenorhabditis elegans Innexin-6 gap junction protein. J Biol Chem 2013; 288:10513-21. [PMID: 23460640 DOI: 10.1074/jbc.m112.428383] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Innexin is the molecular component of invertebrate gap junctions. Here we successfully expressed and purified Caenorhabditis elegans innexin-6 (INX-6) gap junction channels and characterized the molecular dimensions and channel permeability using electron microscopy (EM) and microinjection of fluorescent dye tracers, respectively. Negative staining and thin-section EM of isolated INX-6 gap junction membranes revealed a loosely packed hexagonal lattice and a greater cross-sectional width than that of connexin26 and connexin43 (Cx43)-GFP. In gel filtration analysis, the elution profile of purified INX-6 channels in dodecyl maltoside solution exhibited a peak at ∼400 kDa that was shifted to ∼800 kDa in octyl glucose neopentyl glycol. We also obtained the class averages of purified INX-6 channels from these peak fractions by single particle analysis. The class average from the ∼800-kDa fraction showed features of the junction form with a longitudinal height of 220 Å, a channel diameter of 110 Å in the absence of detergent micelles, and an extracellular gap space of 60 Å, whereas the class averages from the ∼400-kDa fraction showed diameters of up to 140 Å in the presence of detergent micelles. These findings indicate that the purified INX-6 channels are predominantly hemichannels in dodecyl maltoside and docked junction channels in octyl glucose neopentyl glycol. Dye transfer experiments revealed that the INX-6-GFP-His channels are permeable to 3- and 10-kDa tracers, whereas no significant amounts of these tracers passed through the Cx43-GFP channels. Based on these findings, INX-6 channels have a larger overall structure and greater permeability than connexin channels.
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Affiliation(s)
- Atsunori Oshima
- Cellular and Structural Physiology Institute (CeSPI), Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan.
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Silva LL, Marcet-Houben M, Nahum LA, Zerlotini A, Gabaldón T, Oliveira G. The Schistosoma mansoni phylome: using evolutionary genomics to gain insight into a parasite's biology. BMC Genomics 2012; 13:617. [PMID: 23148687 PMCID: PMC3534613 DOI: 10.1186/1471-2164-13-617] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2012] [Accepted: 10/22/2012] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Schistosoma mansoni is one of the causative agents of schistosomiasis, a neglected tropical disease that affects about 237 million people worldwide. Despite recent efforts, we still lack a general understanding of the relevant host-parasite interactions, and the possible treatments are limited by the emergence of resistant strains and the absence of a vaccine. The S. mansoni genome was completely sequenced and still under continuous annotation. Nevertheless, more than 45% of the encoded proteins remain without experimental characterization or even functional prediction. To improve our knowledge regarding the biology of this parasite, we conducted a proteome-wide evolutionary analysis to provide a broad view of the S. mansoni's proteome evolution and to improve its functional annotation. RESULTS Using a phylogenomic approach, we reconstructed the S. mansoni phylome, which comprises the evolutionary histories of all parasite proteins and their homologs across 12 other organisms. The analysis of a total of 7,964 phylogenies allowed a deeper understanding of genomic complexity and evolutionary adaptations to a parasitic lifestyle. In particular, the identification of lineage-specific gene duplications pointed to the diversification of several protein families that are relevant for host-parasite interaction, including proteases, tetraspanins, fucosyltransferases, venom allergen-like proteins, and tegumental-allergen-like proteins. In addition to the evolutionary knowledge, the phylome data enabled us to automatically re-annotate 3,451 proteins through a phylogenetic-based approach rather than solely sequence similarity searches. To allow further exploitation of this valuable data, all information has been made available at PhylomeDB (http://www.phylomedb.org). CONCLUSIONS In this study, we used an evolutionary approach to assess S. mansoni parasite biology, improve genome/proteome functional annotation, and provide insights into host-parasite interactions. Taking advantage of a proteome-wide perspective rather than focusing on individual proteins, we identified that this parasite has experienced specific gene duplication events, particularly affecting genes that are potentially related to the parasitic lifestyle. These innovations may be related to the mechanisms that protect S. mansoni against host immune responses being important adaptations for the parasite survival in a potentially hostile environment. Continuing this work, a comparative analysis involving genomic, transcriptomic, and proteomic data from other helminth parasites, other parasites, and vectors will supply more information regarding parasite's biology as well as host-parasite interactions.
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Affiliation(s)
- Larissa Lopes Silva
- Grupo de Genômica e Biologia Computacional, Centro de Pesquisas René Rachou. Instituto Nacional de Ciência e Tecnologia em Doenças Tropicais. Fundação Oswaldo Cruz - FIOCRUZ, Belo Horizonte, MG, 30190-002, Brazil
- Centro de Excelência em Bioinformática, Fundação Oswaldo Cruz – FIOCRUZ, Belo Horizonte, MG, Brazil
- Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais – UFMG, Belo Horizonte, MG, Brazil
| | - Marina Marcet-Houben
- Bioinformatics and Genomics Programme, Centre for Genomic Regulation (CRG), Dr. Aiguader, 88, 08003, Barcelona, Spain
- Universitat Pompeu Fabra (UPF), 08003, Barcelona, Spain
| | - Laila Alves Nahum
- Grupo de Genômica e Biologia Computacional, Centro de Pesquisas René Rachou. Instituto Nacional de Ciência e Tecnologia em Doenças Tropicais. Fundação Oswaldo Cruz - FIOCRUZ, Belo Horizonte, MG, 30190-002, Brazil
- Centro de Excelência em Bioinformática, Fundação Oswaldo Cruz – FIOCRUZ, Belo Horizonte, MG, Brazil
- Faculdade Infórium de Tecnologia, Belo Horizonte, MG, 30130-180, Brazil
| | - Adhemar Zerlotini
- Centro de Excelência em Bioinformática, Fundação Oswaldo Cruz – FIOCRUZ, Belo Horizonte, MG, Brazil
- Laboratório Multiusuário de Bioinformática, Embrapa Informática Agropecuária, Campinas, São Paulo, Brazil
| | - Toni Gabaldón
- Bioinformatics and Genomics Programme, Centre for Genomic Regulation (CRG), Dr. Aiguader, 88, 08003, Barcelona, Spain
- Universitat Pompeu Fabra (UPF), 08003, Barcelona, Spain
| | - Guilherme Oliveira
- Grupo de Genômica e Biologia Computacional, Centro de Pesquisas René Rachou. Instituto Nacional de Ciência e Tecnologia em Doenças Tropicais. Fundação Oswaldo Cruz - FIOCRUZ, Belo Horizonte, MG, 30190-002, Brazil
- Centro de Excelência em Bioinformática, Fundação Oswaldo Cruz – FIOCRUZ, Belo Horizonte, MG, Brazil
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Clarke GL, Chen J, Nishimune H. Presynaptic Active Zone Density during Development and Synaptic Plasticity. Front Mol Neurosci 2012; 5:12. [PMID: 22438837 PMCID: PMC3305919 DOI: 10.3389/fnmol.2012.00012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 01/30/2012] [Indexed: 12/13/2022] Open
Abstract
Neural circuits transmit information through synapses, and the efficiency of synaptic transmission is closely related to the density of presynaptic active zones, where synaptic vesicles are released. The goal of this review is to highlight recent insights into the molecular mechanisms that control the number of active zones per presynaptic terminal (active zone density) during developmental and stimulus-dependent changes in synaptic efficacy. At the neuromuscular junctions (NMJs), the active zone density is preserved across species, remains constant during development, and is the same between synapses with different activities. However, the NMJ active zones are not always stable, as exemplified by the change in active zone density during acute experimental manipulation or as a result of aging. Therefore, a mechanism must exist to maintain its density. In the central nervous system (CNS), active zones have restricted maximal size, exist in multiple numbers in larger presynaptic terminals, and maintain a constant density during development. These findings suggest that active zone density in the CNS is also controlled. However, in contrast to the NMJ, active zone density in the CNS can also be increased, as observed in hippocampal synapses in response to synaptic plasticity. Although the numbers of known active zone proteins and protein interactions have increased, less is known about the mechanism that controls the number or spacing of active zones. The following molecules are known to control active zone density and will be discussed herein: extracellular matrix laminins and voltage-dependent calcium channels, amyloid precursor proteins, the small GTPase Rab3, an endocytosis mechanism including synaptojanin, cytoskeleton protein spectrins and β-adducin, and a presynaptic web including spectrins. The molecular mechanisms that organize the active zone density are just beginning to be elucidated.
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Affiliation(s)
- Gwenaëlle L Clarke
- Department of Anatomy and Cell Biology, University of Kansas Medical School Kansas City, KS, USA
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20
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Kawano T, Po MD, Gao S, Leung G, Ryu WS, Zhen M. An imbalancing act: gap junctions reduce the backward motor circuit activity to bias C. elegans for forward locomotion. Neuron 2012; 72:572-86. [PMID: 22099460 DOI: 10.1016/j.neuron.2011.09.005] [Citation(s) in RCA: 156] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/07/2011] [Indexed: 11/26/2022]
Abstract
A neural network can sustain and switch between different activity patterns to execute multiple behaviors. By monitoring the decision making for directional locomotion through motor circuit calcium imaging in behaving Caenorhabditis elegans (C. elegans), we reveal that C. elegans determines the directionality of movements by establishing an imbalanced output between the forward and backward motor circuits and that it alters directions by switching between these imbalanced states. We further demonstrate that premotor interneurons modulate endogenous motoneuron activity to establish the output imbalance. Specifically, the UNC-7 and UNC-9 innexin-dependent premotor interneuron-motoneuron coupling prevents a balanced output state that leads to movements without directionality. Moreover, they act as shunts to decrease the backward-circuit activity, establishing a persistent bias for the high forward-circuit output state that results in the inherent preference of C. elegans for forward locomotion. This study demonstrates that imbalanced motoneuron activity underlies directional movement and establishes gap junctions as critical modulators of the properties and outputs of neural circuits.
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Affiliation(s)
- Taizo Kawano
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, ON M5G1X5, Canada
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21
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Yan D, Noma K, Jin Y. Expanding views of presynaptic terminals: new findings from Caenorhabditis elegans. Curr Opin Neurobiol 2011; 22:431-7. [PMID: 22036768 DOI: 10.1016/j.conb.2011.10.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Revised: 09/27/2011] [Accepted: 10/06/2011] [Indexed: 11/26/2022]
Abstract
The unique ability of chemical synapses to transmit information relies on the structural organization of presynaptic terminals. Empowered by forward genetics, research using Caenorhabditis elegans has continued to make pivotal contributions to discover conserved regulators and pathways for presynaptic development. Recent advances in microscopy have begun to pave the path for linking molecular dynamics with subsynaptic structures. Studies using diverse reporters for synapses further broaden the landscape of regulatory mechanisms underlying presynaptic differentiation. The identification of novel regulators at transcriptional and post-transcriptional levels raises new questions for understanding synapse formation at the genomic scale.
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Affiliation(s)
- Dong Yan
- Howard Hughes Medical Institute, Department of Cellular and Molecular Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
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22
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Murakami T, Yang SP, Xie L, Kawano T, Fu D, Mukai A, Bohm C, Chen F, Robertson J, Suzuki H, Tartaglia GG, Vendruscolo M, Kaminski Schierle GS, Chan FTS, Moloney A, Crowther D, Kaminski CF, Zhen M, St George-Hyslop P. ALS mutations in FUS cause neuronal dysfunction and death in Caenorhabditis elegans by a dominant gain-of-function mechanism. Hum Mol Genet 2011; 21:1-9. [PMID: 21949354 PMCID: PMC3235006 DOI: 10.1093/hmg/ddr417] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
It is unclear whether mutations in fused in sarcoma (FUS) cause familial amyotrophic lateral sclerosis via a loss-of-function effect due to titrating FUS from the nucleus or a gain-of-function effect from cytoplasmic overabundance. To investigate this question, we generated a series of independent Caenorhabditis elegans lines expressing mutant or wild-type (WT) human FUS. We show that mutant FUS, but not WT-FUS, causes cytoplasmic mislocalization associated with progressive motor dysfunction and reduced lifespan. The severity of the mutant phenotype in C. elegans was directly correlated with the severity of the illness caused by the same mutation in humans, arguing that this model closely replicates key features of the human illness. Importantly, the mutant phenotype could not be rescued by overexpression of WT-FUS, even though WT-FUS had physiological intracellular localization, and was not recruited to the cytoplasmic mutant FUS aggregates. Our data suggest that FUS mutants cause neuronal dysfunction by a dominant gain-of-function effect related either to neurotoxic aggregates of mutant FUS in the cytoplasm or to dysfunction in its RNA-binding functions.
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Affiliation(s)
- Tetsuro Murakami
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Ontario, Canada
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Bouhours M, Po MD, Gao S, Hung W, Li H, Georgiou J, Roder JC, Zhen M. A co-operative regulation of neuronal excitability by UNC-7 innexin and NCA/NALCN leak channel. Mol Brain 2011; 4:16. [PMID: 21489288 PMCID: PMC3102621 DOI: 10.1186/1756-6606-4-16] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Accepted: 04/13/2011] [Indexed: 11/10/2022] Open
Abstract
Gap junctions mediate the electrical coupling and intercellular communication between neighboring cells. Some gap junction proteins, namely connexins and pannexins in vertebrates, and innexins in invertebrates, may also function as hemichannels. A conserved NCA/Dmα1U/NALCN family cation leak channel regulates the excitability and activity of vertebrate and invertebrate neurons. In the present study, we describe a genetic and functional interaction between the innexin UNC-7 and the cation leak channel NCA in Caenorhabditis elegans neurons. While the loss of the neuronal NCA channel function leads to a reduced evoked postsynaptic current at neuromuscular junctions, a simultaneous loss of the UNC-7 function restores the evoked response. The expression of UNC-7 in neurons reverts the effect of the unc-7 mutation; moreover, the expression of UNC-7 mutant proteins that are predicted to be unable to form gap junctions also reverts this effect, suggesting that UNC-7 innexin regulates neuronal activity, in part, through gap junction-independent functions. We propose that, in addition to gap junction-mediated functions, UNC-7 innexin may also form hemichannels to regulate C. elegans' neuronal activity cooperatively with the NCA family leak channels.
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Affiliation(s)
- Magali Bouhours
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada M5G 1X5
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Swayne LA, Sorbara CD, Bennett SAL. Pannexin 2 is expressed by postnatal hippocampal neural progenitors and modulates neuronal commitment. J Biol Chem 2010; 285:24977-86. [PMID: 20529862 DOI: 10.1074/jbc.m110.130054] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The pannexins (Panx1, -2, and -3) are a mammalian family of putative single membrane channels discovered through homology to invertebrate gap junction-forming proteins, the innexins. Because connexin gap junction proteins are known regulators of neural stem and progenitor cell proliferation, migration, and specification, we asked whether pannexins, specifically Panx2, play a similar role in the postnatal hippocampus. We show that Panx2 protein is differentially expressed by multipotential progenitor cells and mature neurons. Both in vivo and in vitro, Type I and IIa stem-like neural progenitor cells express an S-palmitoylated Panx2 species localizing to Golgi and endoplasmic reticulum membranes. Protein expression is down-regulated during neurogenesis in neuronally committed Type IIb and III progenitor cells and immature neurons. Panx2 is re-expressed by neurons following maturation. Protein expressed by mature neurons is not palmitoylated and localizes to the plasma membrane. To assess the impact of Panx2 on neuronal differentiation, we used short hairpin RNA to suppress Panx2 expression in Neuro2a cells. Knockdown significantly accelerated the rate of neuronal differentiation. Neuritic extension and the expression of antigenic markers of mature neurons occurred earlier in stable lines expressing Panx2 short hairpin RNA than in controls. Together, these findings describe an endogenous post-translational regulation of Panx2, specific to early neural progenitor cells, and demonstrate that this expression plays a role in modulating the timing of their commitment to a neuronal lineage.
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Affiliation(s)
- Leigh Anne Swayne
- Department of Biochemistry, Neural Regeneration Laboratory and Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Ontario K1M 1E5, Canada.
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